The present invention relates to the field of project management and scheduling techniques. In particular, the present invention concerns a novel approach to Theory of Constraints (TOC) buffer graphing, tracking and the management of projects in accordance with TOC techniques.
Various techniques have been used for the management of project scheduling. One of the techniques used to manage such project scheduling is, for example, (Program Evaluation and Review Technique (PERT) chart techniques. PERT chart techniques have been used quite extensively in the management of project scheduling. The PERT technique uses a well known critical path method.
Another technique that has been used for project scheduling and tracking is the Theory of Constraints (TOC). This technique, which is a relatively new approach, is described in detail in the book xe2x80x9cCritical Chain,xe2x80x9d by Eliyahu Goldratt (The North River Press, Great Barrington, Mass. 1997). Some of the key principles of the TOC include the focusing of attention on the critical chain (that chain of events and staff that most determines the delivery interval), eliminating multi-tasking of individuals when building and implementing schedules, and the managing of progress via intervals rather than dates.
In particular, TOC schedules are created by estimating 50% confidence intervals for the individual development tasks of the complete project, i.e. 50% probability of completing the individual task, and then linking them together to create an overall schedule. Because the probability for delivery of the product at completion of the 50% chain is significantly legs than 100% probability, a project buffer, PB, or safety interval, must be added at the end of the critical chain. For non-critical components that feed into the schedule, a feeding buffer, FB, is inserted at the point where the non-critical component links into the critical chain. The xe2x80x9cpaddingxe2x80x9d in the schedule, then, is located at the end of each component chain rather than distributed throughout all tasks.
One of the major drawbacks that exists with presently available TOC-based systems and methods is the inability to quickly and easily generate, update, interpret and understand buffer charts which are suitable for use by all project members in tracking progress to plan.
In particular, presently available tabular systems and methods do not allow project members, or more importantly project managers the ability to readily visually ascertain at a glance, by reference to a chart or model or graphical illustration, when buffer levels are getting too low, such that action can be taken in order to improve delivery results.
Another drawback that exists is the inability to know the actual status of each project component, and especially one that is critical (in order to apply the TOC methodology of identifying and elevating the critical chain). It is difficult, however, to determine this unless one analyzes the detailed schedule and derives the critical chain from dates cascaded by the presently known tools, such as, for example, a software product known as ProChain.
Consequently, there exists a need to quickly and easily generate and update buffer charts by using, for example, a computer system and method. In addition, there exists a need to quickly and easily visually detect when buffer levels are getting too low, so that appropriate action may be taken by project members. Furthermore, there exists a need to provide management with a simple method which may be used to determine a current critical chain.
These needs and others are met using a novel approach to Theory of Constraints (TOC) project management. In the known TOC project management approach, schedules contain buffers or xe2x80x9csafety intervalsxe2x80x9d located at the end of non-critical task chains and at the end of the critical chains. Some consumption of these buffers is likely during development, and progress relative to plan is tracked by monitoring these buffer levels. Furthermore, acceptable buffer consumption may be modeled in a number of ways, including as a linear process over time.
The project management approach of the present invention utilizes feeding and project buffer chart construction and interpretation, and includes a graphical method to identify the effect of critical chain components on the overall project. Specifically, buffer consumption over actual project time is plotted such that one may easily and readily determine, by visual reference to the graph, when buffer consumption crosses a visually discernible minimum consumption line and/or an xe2x80x9calarm linexe2x80x9d which should trigger some corrective management action.
It should be noted that this approach to TOC buffer graphing, tracking and management can be accomplished by the use of computers. For example, several software packages such as Microsoft Project, ProChain (a TOC scheduler) and Microsoft Excel (as well as various other spreadsheet programs) may be employed to automate the inventive methods and techniques disclosed herein.